1) Field of the Invention
The present invention relates to a fluoran compound which is useful as a color forming compound in recording materials such as pressure sensitive and heat-sensitive recording materials. More particularly, the invention relates to crystal of the fluoran compound, to a process for the preparation of said crystal and to the recording materials comprising said crystal.
2) Description of the Prior Art
Pressure-sensitive recording, heat sensitive recording and electroheat-sensitive recording have conventionally been used as systems for recording transferred information through the mediation of external energy, such as pressure, heat or electricity, by utilizing a color reaction between a colorless or pale colored electron donative compound (color forming compound) and an organic or inorganic electron acceptor (developer).
In these recording systems, many fluoran compounds have widely been used as the color forming compound.
For example, 3-N-n-butyl-N methylamino-7-anilino-fluoran compound has been disclosed in Japanese Laid-Open Patent SHO 59-68373(1984).
The fluoran compound represented by the formula (I): ##STR2## has been disclosed as a color developing compound in Japanese Laid-Open patent SHO 60-47066(1985) and described to have a melting point of 101.degree. to 103.degree. C.
When the compound is used as a color developing material for recording materials such as a heat-sensitive recording material and mixed with a developer such as bisphenol A, the compound itself colors dark gray and provides only a dark gray colored (soiled) paper by applying the compound to a paper. Further the compound has a disadvantage of poor storage-stability such as light resistance and leads to difficulty in practical use.